Means for measuring or controlling the frequency or wave length of alternating currents.



0 2 '3: AVAHABLE C .SBIBT.

MEANS FOR MEASURING 0R CONTROLLING THE FREQUENCY OB WAVE LENGTH OF ALTERNATING GURRENTS.

. APPLIGA'I'ION FILED AUG. 2, 1912.

2 SHEETSSHEET l.

Patented Aug. 12, 1913.

G, SEIBT. MEANS FOR MEASURING OR CONTROLLING THE FREQUENCY OR WAVE LENGTH OF Patented Aug: 12, 1913.

BEST AVAILABLE COPY E UNITED. STATES Parana @FhlCE.

GEORG SEIBT, OF SGI-IfiNEBERG, NEAR BERLIN, GERMANY.

MEANS FOR MEASURING R CONTROLLING THE FREQUENCY OR WAVE LENGTH OF ALTERNATING CURRENTS.

1 b all whom it may concern Be it known that I, Gnono SEIBT, a subject of the German Emperor, and resident of Schiinebcrg, near Berlin, Germany, have invented certain new and useful Means for llleasuring or Controlling the Frequency or lVave Length of Alternating Currents, of which the following is a specification.

My invention relates to direct reading instruments for measuring the frequency or wave length of alternating currents of the kind in which the movable part of the instrument receives its energy from fixed coils by induction and is substantially free from the influence of any elastic forces,

The object of the invention is to provide an instrun'ient of the kind above referred to which shall be more sensitive than those hitherto proposed.

In the instrument constructed according to the present invention the movable part is .inductively acted upon. by the fields of fixed coils acting in opposite directions and is shaped and arranged relatively'to the axis of the instrument in-such a manner that of all the planes containing this axis only one divides the armature into'two symmetrical parts when the same is on or assumes a definite position, all the other planes dividing it into unequal parts.-

Figures 1 to 16 of the accompanying drawings illustrate diagrammatically and by way of example various modes of carrying out the invent-ioninto effect. Fig. 1 is a plan view, and Fig. 2 a front elevation of one form of my invention; Fig. 3 is a diagtammatic plan View of another form of my invention; Fig. 4: is a plan, with parts indicated in perspective, and Fig. 5 is a partial plan, of still another form of my invention; Figs. 6 and 7 are'views similar to Fig. 4, showing two further forms of my invention; Fig. 8 isan elevation, with parts in section, illustrating a further construction embodying my invention; Fig. 9 is a plan view showing one form of armature suitable for use in my invention; Fig. 10 shows, upon an enlarged scale, th; central rib of the armature shown in F ig. 9; Fi 11 is a plan view of another form of armature; Fig. 12 is a perspective view of still another formof armature, with its pointer and scale; Fig. 13 is aside elevation, Fig. 14 a diagram of circuits, and Fig. 16 a plan view of the form of my invention employ- Specification of Letters Patent.

Application filed. August 2, 1912. Serial hi0. 712,938.

Patented Ari-g. 12,1913.

ing the armature shown in Fig. 12; and Fig. 1.5 is a plan view of an arn'iature and of a circuit-closer controlled thereby.

Referring to F igs. l and 2 a'and b are two fixed coils arranged approximately 90 0 apart around the axis 0 of the instrument, (Z 18 a movable armature wh1ch consists of apiece of metal closed in itself or of a number of short circuited windings and is mounted on a frame 6 arranged to rotate together with the armature d around the axis 0 and f is an index or pointer secured to the frame (2 and arranged to move in front of a graduated scale 9. Thearmature (Z, the geometrical axis of which is approximately parallel to the axes of the coils (l and b, has the tendency to move under the influence of one of the coils in one direction and under the influence of the other coil in the opposite direction, the sta- 7'5 tio-nary position. of the armature being determined by the relation between the fields produced by the coils a and b. The variation of the fields or of the currents with the frequency may be obtained in various ways,

such as by connecting the coil a to the circuit the frequency of which is to be determinedthrough a condenser h, and the coil 6 through a self induction This form of construction permits of arranging the armature and the plane in which the ends of the fixed'coils are arranged.

The sensitiveness of the instrument and the operative range of the graduated scale may be increased by making the surface 1nclosed by the armature as well as the surface inclosed by each of the fixed coils a and Z), angularly measured, greater than 90.

Two forms of construction of this type are illustrated in Figs. 3, 4 and 5. Fig. 3 which shows an arrangement in which the surfaces of the armature and fixed coils are, angularly measured relatively to the axis of the instrument; greater than 90 and in which the armature is split into two parts d and (Z illustrates a case in which the maximum angle of deviation is theoretically 120, the maximum angle utilized in practlce being, however, about 60 only, since beyond this angle the forces become too small and the indications of the instrument are rendered inaccurate. The arrangement shown in Figs. 4 and 5 in which the surfaces of the armature and fixed coils are,angularly measured relatively to the axis of the instrument about 180' wide is still more sensitive, the maxinuun theoretical angle of deviation reaching 180 and the maximum angle used in practice about 110.

An interesting phenomenon which has been observed in connection with the arrangcment shown in Fig. 4 may now be referred to.

If the coils a and I) in the arrangement shown in Fig.4 are connected in such a manner that their fields have one and the same direction and are in phase with each .armature being so to say in a floating state.

The occurren'ce of the phenomenon above referred to, which takes place in spite of the fact that very strong currents are flowing at the same time through the movable armature, may render the apparatus practically useless if no means were provided for avoiding it. Let us for instance suppose that the instrument is employed for measuring high frequency currents and bear in mind that the phenomenon is caused by the relation between the phases of the fields'and not by the relation between the phases of the currents. It the condenser his made so small that its alternating current resistance is. greater than that of the coil a then the cur rents ofthe coils a and b will have a phase displacement of 180. It is not however certain whether the fields will have the same displacement as the currents, buts'ince this point is determined by the sense in which the coils are wound and by the way they are connected up to the circuit the frequency of which is to b measured, a phase displacement of 180 between'the fields can A be produced by simply interchanging the connections of one. of the fixed coils.

Experiments have shown .thatwhen the.

arrangement illustrated in Fig. 4'is used to measure the frequency of damped oscillations, as produced for instance by means of spark discharges, the values obtained are very inaccurate as-compared with the true values of the wave lengths. The cause of this inaccuracy is that the condenser, the

self inductions of the coils a and b and thin I self induction outside the instrument whichf i'imgemcnt shown in Fig. 6 a displacement serves for connecting. purposes form .together an oscillation circuit wherein free oscillations are indu'red these free oscilla tions having generally a different frequency from that which is to be determined. If the instrument is calibrated by means of undamped oscillations an error is continuously'made when measuring the. frequency of damped oscillations, this error being the greater the stronger the damping of the 0scillation and being also dependent upon the manner of connecting the instrument with v the circuit the frequency of which is to be determined since the .fre uency of the free oscillation is a function di the connection.

In order to overcome the drawback just referred to the free oscillation of the instrument is strongly damped and even made I hardly be practically used where small loss of energy is essential as for instance in wireless telegraphy. For example, a wave meter which consumes 50 watts may he said to be unsuitable for higlrfrequency circuitssince such an amount of energy would be quite suflicient forsignaling over a distance of about 100 kilometers and such a loss could i be justified only in very exceptional cases.

The loss of energy may be reduced by making the resistance to be' inserted in the circuit ofthe coil a very small. With such an arrangement however the ratio between the currents flowing through the fixed coils varies butvery little with the frequency and the divisions upon the scale corresponding to the various frequencies are too close together. This disadvantage is overcome by the arrangement illustrated in Fig. 6 in which .aresistance is is arranged in series with the fixed coil a and a resistance 1 in parallel with the fixed coil 6. Theory and experiment have shown that by these means a graduated scalecan be. obtained in which the divisions are wide apart, in spite of the fact that the watt consumption is substantially decreased, another advantage obtained by the arrangement illustrated in Fig. 6 be ing that with suitable electric donstants the divisions of the graduated scale can in this case be made substantially equal to one another,that is to say the deviations can be made proportional to the wavelengths.

lVith regard to thephase of the fields of the two fixed coils, it is to be pointed out ;-.t it is impossible to obtain with the arof 180 or one of 0, the phase angle lying eithenbetween 0 and 90- or between 90 and 180 without however reaching the outermost limits. The floating phenomenon hereinbefore referred to is also to be observed although to a less extent in the arrangement shown in Fig. 6. It is advisable to lead the currents to the fixed coils a and b in such a manner that the phase displacement of the fields is made as great as possible, that is to say between 90 and 180. If the connections with one of the coils are interchanged it can immediately be noticed that the directive force is considerably reduced and that the moving part has then the tendency to float. It is also to be pointed out that the floating phenomenon can only occur When the armature has a well defined circuit which reaches into the fields of the two fixed coils. If for instance the armature is made in the form of a semi-circular solid disk as shown in Fig. 7 each one of the fixed coils will induce in the movable part mainly separate currents. As can however be easily understood and as experiment shows. this form of construction is forpther reasons disadvantageous. The shortcircuited eddy currents induced by eachseparate coil flow within each iield radially toward the axis of the instrument and then back to the periphery, of the disk with substantially the same strength so that the forces compensate one another to a great extent, only a small difference being left to effect the turning of the movable part. The

use of a well defined circuit which is as free as possible from eddy currents and is under the influence of two fields oscillating in the proper phase has been found to be an important requirement for the success of the instrument. It is also to be noted, that if the instrument is constructed as above referred to no current or hardly any current will flow through the armature after the same has reached its position of equilibrium. In the arrangement illustrated in Fig. l no current whatever will flow through the armature, when the fields oscillate with a phase displacement of 180 and in the arrangement illustrated in Fig. 6 wherein this limit can never be attained the current flowing through the armature can be made very. small if the current is supplied to the fixed coils in the proper manner as above referred to. In order to attain the required sensitiveness the movable part of measuring instruments used in connection with high frequency currents has to be made very light and for this reason it isdesirable to reduce the current in the armaturc as much as possible so as to prevent overheating.

Fig. 8 illustrates modified form of con 'struction which is still more sensitive and the scale of which has a wider range. In thls form of construction the fixed coils a and Z) are arranged slightly inclined tothc surface of the armature (Z, and the increased will be greater when the field intensity de-,

creases than when the intensity is constant, the consequence thereof being that with a definite variation of the freruiency the arrangementof the inclined coils will. give a greater variation of the deviation angle. The angular relation of the coils a, Z; of Fig. 8, and their effective areas are the same as shown in Figs. 5, 6, and 7, that is to say,

these coils are located diametrically opposite each other, and each is semicircular.

Referring now; to the form of the movable armature it is desirable to reduce the weight of the same as much as possible and I have found that a sheet of aluminum 0.05 to 0.3 millimeters thick answers this purpose very well.

I have just pointed out that it is desirable to increase the scnsitivenes of the instrument by making the nnwalne part of a thin sheet of aluminium. This mode of construc tion however has the disadvantage that the part in (see Fig. 9) of the armature is liable to bend. In order to avoid this drawback the sheet is formed with a rib as shown on ,an enlarged scale in Fig. 10, and an insulated'reinfored arm n is provided between the parts 0 and m of the armature, shown in Fig. 9. Instead of forming the sheet with a rib,'as shown in the drawing the same may be T-shaped or be bent into a tubular form or be'reinforced in any other suitable way. Thefreinforcement of the armature more especially required in the case where the armature has a surface angular-1y greater than that of the fixed coils, which construction I have found increases the sensitiveness of the instrument for instance if the surface of the armature is increased by 15 on each side (see- Fig. 11) the resistance in series with thecoil a can be reduced by half without in any Way afiecting the range of the scale. In the arrangements hereinbefore referred to the fixed coils, a and Z) serve for the purpose of inducing a current in the inorable armature d and also for the purpose of producing together with the induced current the turning force which acts upon the armature. According to a modification of the invention these two functions are separated and fulfilled by separate coils. A'form of construction embodying this feature is illustrated. in Figs. 12 to 14:. The coils a and I) are semi-circular as in the construction herewhich'exert a torque upon the portions r r Iulm l inbefore referred to and induce a current in the armature. They do not however exert any or any appreciable mechanical folcupon the same sirlcethe portions 1' r of the armature, are sul'istantially removed from the proximity of said coils. in addition to the latter coils I provide coils A and B which I arrange in the proximity of the portions r r o-t the armature. These coils are intended to produce fields as uniform as possible and they may be made semicircular but preferably completely circular so that they shall not induce any currents in the armature. Fig. 'lliis diagrammatic plan view indicating circular superposed coils A, B,

and semicircular coils 0,?) arranged as in the constructions described above. With such an arrangement the energy consumed-by the instrument can be substantially reduced and the sensitiveness increased since the numbers oi? the windings of the coils A and Bmay be considerably increased without in any Way incrcasin the watt consumption. In the case of high frequency currents it is advantageous to form the coils oi? cord wires that is to say, of cables having a plurality of wire strands.

The instrument forming the subject mat ter of the present invention may also be used relay or like controlling device. In

, use the conducting pointer f connected m 1 the movable armature is arranged to ab: a ainst the fixed contacts when overstcmiing or falling short of a. predetermined improved instrument is so shaped that of allthe planes passing through the axis of the instrument in Fig; 1) only one divides the armature into two symmetrical parts. Thus in Fig. 1, the axial plane-biscctin'g the angle o the t nine 0 is the only axial plane relatively to which the armature (Z is sym-- metrical, and all other planes passing through the axis a will divide the armature (K into two unequal parts.

" claim as my invention:

..- J LTi instrument for measuring c. checkucncy. The pivot of the movable arma-' ing the frequencyor wave length of alternating currents, comprisingin combination a pivot, a movable armature having a semicircular portion, a U-shaped portion projecting on one side of saidsemi-circular portion and another U-shaped portion projecting on the other side of the semi-circular ortion, two fixed coils ar 'anged in the proximity of the semi-circular port-ion of the movable armature, two fixed coils arranged in the proximity of the middle parts of the U-shaped portions of the movable armature, an index mounted on the pivot and a graduated scale, whereby the fixed coils arranged in the proximity of the semi-circular portion of the movable armature induce a current in the latter and this current together with the field of the coils arranged in the proximity of the middle parts of the U-shaped port-ion produce a torque which causes the. rotation of the movable armature, as set forth.

2. An instrument for measuring or check ing the frequency or wave length of alternating currents, comprising fixed coils and a movable armature influenced inductively by said coils and so arranged that only one or the planes passing through the axis of the instrument will divide the armature into two symmetrical partswhen the same occupies a definite position, all other axial planes dividing it into unequal. parts, the surface of the movable armature as well as the surface of each of the fixed coils through which the lines of force pass, being greater than 90, measured angularly relatively to the axis of the instrument.

3. An instrument. for measuring or checking theirequency or wave length of alternating currents, comprising fixed coils and a movable armature influenced inductively by said coils and so arranged that only one of the planes passing through the axis of the instrument will divide the armature into two symmetrical parts when the same occupies a definite position, all other axial planes dividing it into unequal parts, the surface of each of the fixed coils through which the lines of force pass, being about 180 wide, measured angularly relativelyto the axis of the instrument.

In testimony whereof I have signed this specification in the presence of two subscrib- 

